Stop joint for fluid filled cables



June 14, 1938. 1 EMANUELI STOP JOINT FOR FLUID FILLED CABLES uehAttorney Inventor: Lut@ Ea si'` b H/f/fN/H/N/H/N/...f//l Y/f d Feb. 17,1958 presents many difficulties.

Patented June 14, 1938 UNITED STATES- aliases PATENT OFFICE LuigiEmanueli, Milan, italy assigner to Societa Italiana Pirelli, corporationof Italy Application February l'i,

1938 Serial No. 3.91,@

'l' Clanisu (Cl. MSH-268i Stop-joints are employed. in fluid filledcable systems for the purpose of subdividing the cables into sectionssoias to limit the hydrostatic head oi the impregnating liquid on theenclosures or sheaths of the connected cable lengths, and for thepurpose of permitting the impregnatng dielectric or liquid to flowbetween the hollow core, oi the ca-I ble conductor and an externalsource of supply, such as a variable capacity reservoir 'sealed 'againstthe admission of air. They are also employed te segregate one sectionfrom another as regards the liquid dielectric so that in the event alea. in one section, the liquid wili not be drained from theconnected/section or sections.

On account of the fact that there is a difference of potential betweenthe conducto and the surrounding metal parts, the probiere effectivelyinsulating them one from the otner The greater the dit" ference ofpotential, the greater are the diiilculties oi' manufacture and greatercare must be exercised in making an installation. Prior to my presentinvention, numerous installations of fluid filled cable had been made inthe United States and in countries foreign thereto operating at 132,000volts, and in Nestor all cases the cables were provided withstop-joints, for example of the type shown in my Patent 1,698,051 datedJanuary 8, 1929 or that shown in the Eby Patent 1,819,882 dated August18, 19'11. l

.The present invention is directed to a stop-joint for underground cablesystems and is especially -designed to operate under very high voltages.Joints made in accordance with my invention are in successful operationat the present timegand, with the connected cables, are operating at thehighest voltage ever used in a commercial underground cable system. Asan illustration, but not as a limitation of my invention, the joint'iilusn trated herein is designed to operate at 226,008.

volts. In order that some idea may be had of the` size of such joints asare here illustrated, it

may be stated that the joint casing is approz/:i-av

mately 101/2 feet long with an approximate siax muni diameter of 151/inches. It is to be andere stood, however, that the dimensions given arenot limitations since a change in operating voltage er a change in theinsulating materials used, or both, may and in most cases would result achange of dimensions.

In such a stop-joint, a great mass of fibrous insulation is applied tothe joint parts in order that they may withstand the tremendous vetta-geto which they are subjected. The vaine of auch material as an insulatingmedium depends to a very great degree upon how thoroughly gas rem movedand hor,Y completely the material. is iinprega-.ated with liquiddielectric, as degosiiied oil, for example, and how completely ali voidsare filled with the liquid, or both. inver directed more specifically tothe Ways and ior ensuring eornpiete filing of the voids or witi n thejoint and the proper insuiatioo an i iproved ne drawing whichillustrates on Fig. 2 is an axial sectional view oi appro one-half cithe joint; Fig. 3 is a perspective view of a portion or one end of thejoint, and Fig. i is a perspective Viewof a portion ci a beit comprisingparallel tubes of insulating material.

E and 'l indicate the cables, the conductors of which are hollow andunited by the two-part connectors 8 and 9 and the flexible member l0. Asboth halves of the joint are alike, a description. of one of them willbe sufficient. The connector 8 supports the small end of'a cone-shapedinsulator Il, its outer end being supported by the head l2, the latterbeing secured to the end meinber i3 of the joint casing. I4 indicatesthe factory applied insulation on the conductor and surrounding it arelayers of fibrous insulation I5 arranged in step formation and alllocated Within ythe cone insulator.

and lulniecgtent filling by the liquid dielectric of 45 whichdegasii'ied oil may be taken as an example.- The casi is made halves toof as-i sembly a W the parte or the connector a u ted by the flexiblemember i0, the plane ci t of the casing being axial. The parte of thecas 5@ ing are soldered or otherwise secured together; Adjacent ends ofthe screen i@ are n'ietz'tl rings Ei? ci which one is shown. Each ofthese is com neet-ed to a conductor as by a lead and screw ige and henceat the same potential. 555

function of these rings is to increase the perfor'in tion tension in theregions near the two ends oi the connector which are particularlysubject to electrical discharges. Each oi the rings is separatelyinsulated before application to the joint structure and is supportedinternally by the enlarged end or a connector part such as ii.

Over the cone insulator is applied bands of ilbrous insulating material2li, either in the form of layers or laminations of tape or sheetmaterial, a small amount of fibrous tape being first applied over theportion of the cone insulator adjacent the ring i3 to enlarge thediameter and make the outer surface more nearly cylindrical. Anadditional wrapping or band of iibrous insulating material 2l is appliedover the screen iii and over a part of the insulator ill). Anotherreinforcing insulation, indicated at 2t, is applied over` the insulation2t. Surrounding the insu.- lation 2li on the cone are belts 23 and 24,each comprising small tubes 25 made of insulating material, all strungtogether or held in place to form an annulus by cords 2t which passcompletely through them. By passing the cords through the tubes andpermitting the tubes to make contact along their sides, the necessity ofindividually anchoring each tube is avoided. After the belt is applied,the ends oi the cord or other fastening means are tied or otherwiseunited. It is desirable to use two such cords located near the ends ofthe tubes to prevent relative displacement thereof. By making the tubesrelatively small in diameter andso numerous that they contact with eachother along their peripheral surfaces in axial planes, they form anannulus which presents relatively smooth internal and external surfacesand because of that fact, they snugly t the supporting surface and alsoform or define an outer surface over which relatively thin insulationmay smoothly and evenly be wound or applied in layers to form a cylinderas contrasted to an irregular surface composed of high and low spots aswould be the case if the tubes were widely spaced. it is advantageoustol slightly bevel the internal ends of the tubes so as to ensure smoothsurfaces and free passage ci the liquid therethrough. The right handbelt 23 serves as a support for one end of the overlying cylindricalbody of brous insulation 2 and also as a means to permit the passage ofliquid dielectric axially therethrough. The left hand belt 24 supportsthe right hand end of a tubular body of insulation 28, the opposite endof which is supported by the rigid cone insulator. It will be observedthat there are liquid containing spaces or chambers such as 29, 30 and3i. If it were not for the belts of tubes, they would be wholly orlargely shut off from the liquid dielectric within the joint casing andas a result the effective insulation would be greatly decreased.

32 indicates a relatively long cylinder of insulating material which issupported ln concentric relation with the axis of the joint by spacedbelts 33 and 34, each comprising parallel tubes of insulating materialas best shown in Fig. i and previously described. The tubes of belt 33serve to convey liquid dielectric between the space or chamber 35 andspace or chamber 3U. The tubes of the right hand belt 34 serve 'toconvey liquid dielectric between the annular space or chamber 3D and theoutermost annular space or chamber 3b. From Fig. 3, it will be seen thatthe belts 24 and 33 are located in the same plane with the cylindricalbody of insulation 28 beatadas@ tween them. rihe tubes of the inner belt24 are desirably slightly smaller in diameter than those of the outerbelt and fewer in number because the diameter of the joint in this planeis less. The belts by reason of their construction are exible so thatthey may easily be wrapped around the parts o the joint and because thetubes are united by flexible means such as cords, it becomes a simplematter to secure them in place. Liquid dielectric is supplied to andreceived from the outer chamber 36 oi the joint casing by the iitting 3lcarried by the outer main casing 38 of the joint. Liquid dielectric isadmitted to and received from the hollow core cable by the iitting i6mounted on the end cap of the joint casing. rlhis fitting when the cableis in service is connected to a variable capacity reservoir tocompensate for variations in volume of the liquid in the core of theconductor. The liquid dielectric flows into and out of the hollowconductor 39 through the connector and through the space between theinsulation on the conductor and the cone into the end chamber 40 of thejoint casing. The joint casing is also provided with a tting di wherebythe lling and draining thereof is facilitated.

As previously indicated, the belts act as supports for masses ofinsulation and also serve as channels to convey liquid dielectric fromone more or less isolated space or chamber' to another or others and inso doing prevent the formation of dry spaces which otherwise would beonly imperfectly filled with liquid.

it is a characteristic feature of my improved construction that thesolid or mass insulation outside of the cone insulators is arranged inthe form of tubular elements and that between certain of the elementsare arranged flexible belts which serve the double purpose of supportingthe outer or surrounding elements and affording dennite passages for theliquid. The belts form a unit assembly and being iiexible conform to theshape of the body encircled thereby and are easily secured in place. Dueto the numerous tubes of which each belt is composed, there is no danger'of a stoppage of the free circulation of the liquid dielectric. Thetubes being assembled and united to each other as they are, there is nodanger of a workman making an error in the application of the belts.

Attached to the end head i2 is an end bell 42 which flares outwardly tothe wall of the casing 38 and is secured thereto. The purpose ci thisbell is to provide voltage gradients both radial and lateral which arewithin the safe working Values of the several insulating materialsemployed. The end bell is provided with a number of grooves or notches43 which establish connection between the chamber supplied by thefitting 3l? and the central part of the joint casing.

The center of the joint is provided with a thick covering of fibrousinsulation 44 over which is applied a relatively thin tubular body ofinsulation 45, the latter being separated from the metallic casing ofthe joint by an annular space to which the liquid has free access.

IThe use of iexible belts has been described in connection withstop-joints as they have great utility in connection therewith but theymay also be used with advantage in other types of joints where it isimportant to keep the solid insulation fully exposed to the action ofthe liquid dielectric.

The wrappings of fibrous insulating tape and sheets are referred toherein as solid insulation to distinguish them from the liquiddielectric. In

some instances, the sheets or tapes arewound in layers directly on someinterior part and are immovable when once applied, While in otherinstances, as the cylinder 28, for example, the cylinders are wound andthen slipped endwise into place in the end bells 42. It will be apparentthat flexible belts of the character described are not limited in theiruse to cable joints since they may be'used wherever desirable inelectrical apparatus as a means for insulating one conductor means fromanother and where it is important to maintain complete lling andcirculation of liquid dielectric. It will also be apparent that whilethe greater part of the liquid dielectric will flow back and forththrough the tubes as it expands and contracts, a certain amount will owthrough the small spaces dened by the periph-- eral surfaces of thetubes and the solid insulation upon which the belt is supported orbetween said surfaces and the wrapped-on insulation covering andsupported by the tubes.

The belts are so constructed as to have sufriciently good dielectricstrength in a radial direction, that is toward the joint casing, havingat the same time passages or channels for the liquid which greatlyfacilitate the impregnation of the internal parts of the joint casing.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. An electrical conductor means, a metallic enclosure therefor, a llingof liquid dielectric for the enclosure, and a exlble belt comprisinginsulating tubes arranged side by side and surrounding the conductormeans and located between it and the enclosure and through which thedielectric is free to ow.

2. An electrical conductor means, a metallic enclosure therefor, a llingof liquid dielectric for the enclosure, insulating tubes surrounding theconductor means and located between it and the enclosure and throughwhich the liquid dielectric is free to ow, and exible means located nearthe ends of the tubes for holding them in side by side relationship toform a flexible belt and for securing the belt around the conductormeans.

3. A cable joint comprising electrically connected conductors, bodies ofliquid impregnated insulation of cylindrical form enclosing theconductors, the ends of certain of the lbodies being in spaced relation,a flexible belt arranged between one of the bodies and that immediatelythereunder to support the former, the belt comprising a relatively largenumber of small diameter tubes arranged in close side by side axialarrangement and united to prevent relative displacement, a sealed casingenclosing the parts of the joint, and a filling of liquid dielectric forthe casing which permeates the bodies and flows freely through the tubesas the liquid expands and contracts with temperature changes.

4. A cable joint comprising electrically connected conductors, a body ofinsulation surrounding one of the conductors, a exible belt surroundingand supported by the body, the belt comprising a relatively large numberof small insulating tubes arranged side by side and extending parallelto the axis of the conductor, a cylindrical body of solid insulation,one end of which is supported by the belt, a second belt of similarconstruction concentric with the first and supported by the cylindricalbody, a second cylindrical body of solid insulation surrounding thesecond belt and supported thereby, the bodies being in radially spacedrelation with liquid containing chambers between, a sealed casing forthe joint parts, and a nlling of liquid dielectric for the casing whichflows into and from the chambers through the tubes as the liquid expandsand contracts due to temperature changes.

5. A cable joint comprising electrical conductors arranged end to end, aconnector for uniting them electrically, a body of solid insulationsurrounding one of the conductors, a flexible bel*u comprising aplurality of insulating tubes arranged side by side, means for flexiblyuniting the tubes and securing them over the body of solid insulation, abody of solid insulation surrounding the belt and supported thereby, acasing for the joint, and a lling of liquid dielectric for the casingwhich circulates through the tubes and prevents the formation of voids.

6. A belt for the purposes described comprising a plurality ofrelatively small tubes of insulating material having perforations neartheir ends, and means for uniting the tubes to form an annuluscomprising cords of insulating material which extend through theperfor-ations, the ends of the cords being united to secure the belt inplace.

7. A cable joint comprising conductor means, a metallic enclosuretherefor, a filling of liquid dielectric for the enclosure, and aflexible belt comprising insulating elements disposed side by side inaxial relation and surrounding the conductor and exible insulating meansfor securing the belt as a unit assembly in position around theconductor.

LUIGI EMANUELI.

